The former Cabinet Minister has announced he will deliver his valedictory speech in early May.
"It has been a privilege to be elected by the people of New Zealand to represent their interests in Parliament for the last 23 years," Parker said in a statement.
"I leave enthusiastic for New Zealand and for the New Zealand Labour Party."
Parker, who has been an MP since 2002, twice held the role of Attorney General, from 2005-2006, and from 2017-2023.
He also held the Trade, Revenue, Economic Development, Associate Finance, Climate Change, Energy, Environment, State Services, Transport and Land Information ministerial portfolios.
In a statement, he said he had served in his roles "to the best of my ability".
In his first stint as environment minister he legislated the Emissions Trading Scheme, and in his second spearheaded the overhaul of the Resource Management Act (the latter was repealed by the current government).
As trade minister, Parker signed New Zealand up to the Comprehensive and Progressive Agreement for Trans-Pacific Partnership, and ratified the PACER Plus agreement.
He resigned from his revenue portfolio ahead of the 2023 election, due to Labour ruling out a wealth tax policy.
First elected in 2002, after winning the Otago seat, Parker has been a list MP since 2005.
He was also Labour's Deputy Leader from 2013-2014, under David Cunliffe, and later ran to replace Cunliffe as leader but came third behind Andrew Little and Grant Robertson.
He currently serves as Labour's spokesperson for Foreign Affairs, and as Shadow Attorney General.
Parker said he left "enthusiastic for New Zealand and for the New Zealand Labour Party," and thanked his colleagues and wished them well.
"I was a serial entrepreneur before coming to Parliament and have been an agent for change while here. I will return to the private sector and continue building a prosperous and egalitarian nation," Parker said.
More to come...
